Perimetry Test (Visual Field Testing) for Glaucoma
A perimetry test (visual field test)
measures all areas of your eyesight, including your side, or peripheral,
To do the test, you sit and look inside a bowl-shaped
instrument called a perimeter. While you stare at the center of the bowl,
lights flash. You press a button each time you see a flash. A computer records
the spot of each flash and if you pressed the button when the light flashed in
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At the end of the test, a printout shows if there are
areas of your vision where you did not see the flashes of light. These are
areas of vision loss. Loss of peripheral vision is often an early sign of
Why It Is Done
A perimetry test can help find
certain patterns of vision loss. This may mean a certain type of eye disease is
present. It is very useful in finding early changes in vision caused by nerve
damage from glaucoma.
Regular perimetry tests can be used to see
if treatment for glaucoma is preventing further vision loss.
The amount of peripheral vision loss is
linked to the amount of optic nerve damage.
A person with
open-angle glaucoma may have a certain pattern of
vision loss. Vision loss first occurs farthest from the center of the eye,
usually on the nose side first. As the disease gets worse, larger areas of
vision loss are seen on a perimetry test. The area of the eye that gives you
the sharp, central vision (macula) you use for reading is usually damaged later
in the disease. This can lead to total blindness.
What To Think About
A perimetry test is a good test
to find vision loss caused by glaucoma. A perimetry test makes a detailed
record of your visual fields. Baseline information, descriptions or drawings
can be compared with future test results.
A perimetry test can be
done quickly, but it may take more than 45 minutes when both eyes are